Sport shoes such as ski boots must fit tightly on the user's lower extermity. During certain maneuvers, with a ski boot in turning a ski, for example, the tightness of the fit needs to be greater than during other times when the forces transmitted between the lower extremity and the ski are not as severe. Generally, the force required for a carved turn is applied to a ski using forward, neutral or rearward leverage depending on the conditions and the performance required. Most turns are initiated with forward leverage to increase control of the ski tip. Forward leverage places the most severe part of the reversed camber toward the tip of the ski; however, if forward leverage is maintained throughout a turn, the tip acts as a brake and causes excessive chatter. For this reason, as soon as the tip establishes the desired arc of the turn, the pressure on the ski is typically moved to the center of the ski or a position of neutral leverage. During certain maneuvers as during long radius turns on relatively flat terrain or soft snow, rearward lean against the ski boot cuff is used to increase leverage on the ski. On steeper terrain, turns are often ended with rearward leverage to provide acceleration. Lean against the rear cuff of the ski boot is also applied during the completion of the arc of a turn in slalom racing.
In the past, it was typical to tighten the ski boot as much as possible, and physically bearable, to prevent or at least minimize relative movement of the lower extremity in the boot at times when maximum force and leverage are transmitted between the foot, the leg and the boot. As a practical matter, such a fit is excessively tight during most other times and quite frequently is uncomfortable, can lead to numbness and in extreme cases, can result in injuries. Thus, a compromise is frequently reached by tightening the boot on the foot and leg more than is necessary for the small forces that are applied and less than is desired to prevent relative movement of the foot and leg in the boot when large leverage forces are applied. Consequently, the fit of such ski boots is almost always other than what it should be.
The problem has been recognized in the past in connection with ski boots where the exerted leverage forces are especially large and the required tightness of the fit for extreme maneuvers is typically unbearable for any length of time. This inventor has developed dynamic fitting systems which temporarily increase the tightness of the fit of the ski boot on the foot in response to certain skiing maneuvers. In these disclosures, the boot, or at least a portion of the boot increases in tightness in response to a forward lean of the skier.
Analysis of certain skiing maneuvers has shown that the ski boot should tighten in both forward and rearward lean from the normal skiing position. Particularly in competitive skiing when weight shifting is extreme and forward and rearward leverage is applied to the ski boot cuff to change the camber of the ski, dynamic tightening is essential to transfer the maximum energy to the ski tip and tail.